The proposed Program Project Grant entitled "Biology and Transplantation of Human Stem Cells" is a focused, integrated effort to characterize the hematopoietic stem cell and to develop methods for ex vivo selection and expansion of stem cells suitable for human clinical transplantation therapy. Basic research studies are proposed in Project 1 to develop in vitro methods for characterization of the hematopoietic stem cell at the single cell level and to determine the effect of stromal components, stromal-derived factors and cytokines on primitive progenitor growth. To demonstrate their ex vivo expansion potential, human primitive progenitors will be retrovirally marked and transplanted into sheep. In Project 2, related basic research studies are proposed to define optimal in vitro conditions for differentiation, commitment and maintenance of primitive natural killer cell progenitors as well as maintenance of multineage (myeloid/lymphoid) progenitors using single cell assays and retroviral marking studies. These two basic research projects form the foundation for a series of clinical trials employing selected and expanded primitive hematopoietic progenitor populations in autologous and in umbilical cord blood allogeneic transplantation. In project 3, autologous transplant therapy for chronic myelogenous leukemia (CML) will be performed using mobilized progenitor populations from marrow or peripheral blood. In vitro studies are proposed to characterize progenitor populations obtained in CML patients after priming and to develop methods for ex vivo selection, expansion, retroviral marking and transplantation of hematopoietic subpopulations enriched for benign progenitors. In additional studies, IL- 2 activated natural killer cells (ANK) will be tested to prevent relapse following autologous transplantation therapy for multiple myeloma will be assessed. The effects of priming on mobilization of peripheral blood progenitors as well as the development of ex vivo methods for selection and expansion of benign primitive progenitors from the peripheral blood multiple myeloma patients will be explored. Sensitive molecular genetic techniques will be applied to detect the presence of contaminating myeloma cells in the stem cell inocula as well as in transplant recipients. Retroviral marking studies are proposed to determine the role of transplanted progenitors in reconstitutional of hematopoiesis and recurrence of myeloma. In Project 5, progenitor content and growth potential of umbilical cord blood cells will be characterized and compared to that of adult marrow and peripheral blood cells. Methods for expansion and retroviral marking of umbilical cord blood progenitor populations will be developed. Clinical trials are proposed assessing the efficacy of umbilical cord blood and of expanded umbilical cord blood progenitor populations to reconstitute hematopoiesis after related and unrelated donor transplantation therapy for patients with lethal hematologic malignancies. Retroviral marking studies will be used to determine the contribution of progenitors to reconstitution of the hematopoietic compartment following transplantation. Cores supporting administration (Core A), biostatistics (Core B), an organized approach to procurement and storage of samples (Core C), retroviral marking, detection of retrovirally marked cells and detection of cells containing the BCR/ABL gene abnormality (Core D) are integral to the project. This tightly interrelated program project will greatly expand our understanding of human hematopoietic stem cell biology and accelerate the transition from basic stem cell biology studies to the application of stem cell transplantation therapy for a variety of malignant diseases.